The Sofitel Chicago Water Tower is a
33-story luxury hotel on a tight corner in the city's Gold
Coast district. It features 415 guestrooms above a four-story
base. Excavating Chicago's soft mud was a challenge because
sidewalls can move up to 8 in.

Creating a base building that offered open spaces
for a ballroom and lobby while supporting the weight of a
concrete tower also proved challenging.

Chicago-based Tribco, the concrete contractor,
created an elaborate support grid on the sixth floor, including
massive 7-ft.-wide by 7-ft.-deep girders to transfer loads.
Precautions against possible settlement due to the tower's
weight threatened the schedule as engineers tried to block
base-building progress until the tower reached the 26th floor.

Designers and contractors delinked the base
and tower with a 4-ft.-wide pour strip cast into a floor slab.
Any tower settlement cracks were drawn to the strip.
The project involved the unique application of materials.

French designers joined two public areas in
the building's base by installing solid glass stair treads.
There was no margin for error.

West Saint Paul, Minn.-based HKL Cladding Systems,
the curtain wall contractor, faced an exceptional challenge
on the south face: No two glass panels were the same size.
Chicago-based architect Teng & Associates provided 3-D
coordinate points to size each panel.

Site Challenges

Site challenges were exceptional, as the project was on a
small lot flanked by a parking garage, supermarket and the
traffic these attract. Each of the 30 or more ready-mix trucks
per day was under pressure to delivery loads and leave. When
construction reached the 10th floor, deliveries of windows
and drywall congested the site still more.

Tribco saved space by using the tower crane and bucket, instead
of a pump, to place the concrete. Also, a drive-through was
set up in which ready-mixed trucks drove in, unloaded and
departed.

Installing temporary power was a potential site clogger.
Instead of locating it adjacent to the building base, which
would have interfered with deliveries, electrical equipment
was located in a small pedestrian alley on the north side
of the site.

The jury said, "The team really broke the mold of conventionality
on this one. No two glass panels are the same size, which
is a testimony to the fact that the people building this project
really wanted to skate outside the lines. This project took
a lot of coordination, which was a huge construction challenge."